Parasite identification, succession and infection pathways in perch fry (Perca fluviatilis): new insights through a combined morphological and genetic approach

Abstract

Identification of parasite species is particularly challenging in larval and juvenile hosts, and this hampers the understanding of parasite acquisition in early life. The work described here employs a new combination of methods to identify parasite species and study parasite succession in fry of perch (Perca fluviatilis) from Lake Constance, Germany. Classical morphological diagnostics are combined with sequence comparisons between parasite life-stages collected from various hosts within the same ecosystem. In perch fry at different stages of development, 13 different parasite species were found. Incomplete morphological identifications of cestodes of the order Proteocephalidea, and trematodes of the family Diplostomatidae were complemented with sequences of mitochondrial DNA (cytochrome oxidase 1) and/or nuclear (28 s rDNA) genes. Sequences were compared to published data and used to link the parasites in perch to stages from molluscs, arthropods and more easily identifiable developmental stages from other fishes collected in Lake Constance, which both aided parasite identification and clarified transmission pathways. There were distinct changes in parasite community composition and abundance associated with perch fry age and habitat shifts. Some parasites became more abundant in older fish, whereas the composition of parasite communities was more strongly affected by the ontogenetic shifts from the pelagic to the littoral zone.

Diversity, specificity and speciation in larval Diplostomidae (Platyhelminthes: Digenea) in the eyes of freshwater fish, as revealed by DNA barcodes

“…These 29 sequences differ from those of other studies by mean K2P = 6.2% (range 0.51-12.1%; after removing the problematic 3 0 %50-bp motif, by mean K2P = 4.15% (range 0.5-7.9%)); including the 29 sequences led to an implausible result even excluding the problematic motif. Most authors working in the region have encountered both novel ITS sequences and some identical to those published in previous studies of Diplostomum (Rellstab et al, 2011;Behrmann-Godel, 2013;Georgieva et al, 2013;Haarder et al, 2013;Blasco-Costa et al, 2014, present study, but see Cavaleiro et al, 2012), but no matches to the 29 Diplostomum ITS1 sequences from Anandan (2004, op. cit.).…”

“…(v) The CO1 from cercariae from R. cf. peregra (Germany) matched that of cercariae from Radix auricularia and metacercariae from Rutilus rutilus (Germany) sequenced by Behrmann-Godel (2013), and of metacercariae from Cyprinus carpio (Spain, Pérez-del-Olmo et al, 2014), all belonging to Diplostomum sp. Q.…”

“…PhD thesis. University of Aberdeen, UK) that have been used in a number of studies (Nolan and Cribb, 2005;Locke et al, 2010a;Cavaleiro et al, 2012;Behrmann-Godel, 2013;Georgieva et al, 2013;see Supplementary Data S2). The final (3 0 terminal) 50-53 bp of 29 of these sequences (AY386134-63) aligned best with ITS2, although the sequences are purportedly from ITS1.…”

“…Aside from their importance in fish health, eye-dwelling diplostomids are frequent subjects of evolutionary and ecological studies (e.g., Ballabeni and Ward, 1993;Kalbe and Kurtz, 2006). However, diplostomid metacercariae are difficult to identify morphologically and molecular methods are often used to distinguish species (Locke et al, 2010a,b;Rellstab et al, 2011;Cavaleiro et al, 2012;Behrmann-Godel, 2013;Chibwana et al, 2013;Désilets et al, 2013;Georgieva et al, 2013;Ndeda et al, 2013;Blasco-Costa et al, 2014;Pérez-del-Olmo et al, 2014;Kuhn et al, 2015;García-Varela et al, 2015;Mateos-Gonzalez et al, 2015;Otachi et al, 2015). Consequently, DNA sequences from diplostomids are accumulating from all over the world, particularly from Diplostomum spp.…”

Molecular and morphological evidence for three species of Diplostomum (Digenea: Diplostomidae), parasites of fishes and fish-eating birds in Spain

“…In this study, we used the molecular framework and the recently generated genetic datasets for Nearctic and Palaearctic species of the genus [1,6,13] to investigate species diversity of Diplostomum in birds and fishes sampled opportunistically in three regions in the northern and southern Spain. We provide the first molecular evidence associated with descriptions of the hologenophores sensu Pleijel et al [14] for three species of Diplostomum.…”